Heat skillet over medium-high. Cook sausage and onion until browned. Drain grease.
Lower heat to medium-low. Add garlic, Alfredo, marinara, seasoning, and red pepper flakes. Stir well.
Stir in frozen tortellini, coat fully in sauce. Cover and cook until tender.
Top with mozzarella. Melt in oven at 400°F or cover on stove until gooey.
Sprinkle parsley, serve hot.
